Pathogenesis of calcium oxalate stones is under study. Serum PTH and 1,25(OH),2D3 and nephrogenous cyclic AMP, are being measured, along with response to low calcium diet and thiazide in patients with idiopathic hypercalciuria. Urine saturation and crystal growth inhibition are being measured in stone formers, in response to various forms of treatment. The macromolecular urinary crystal growth inhibitors are being purified in order to determine their composition and their mechanisms of action.